Applicant's co-pending patent application, No PCT/AU02/01716, the specification of which is included herein by reference, describes a poppet type valve for reverse pulse cleaning of filter elements, using a reverse pulse of relatively low pressure air. The low pressure high volume pulse provides an efficient cleaning pulse which has a wide range of applications in the filter cleaning industry. The valve described in the specification employs a high pressure operating fluid for opening and closing the valve.
The efficiency of a reverse pulse cleaning system is determined by a range of factors including, the volume flow rate of the reverse pulse, the peak pressure of the pulse, and the time taken to discharge the pulse volume. In other words, it is the form of the pressure wave which determines the efficacy of the pulse. Generally it is the initial blast of air which achieves the cleaning of the filter, and air which flows through the valve after that initial pulse has discharged will be substantially wasted. It is thus desirable that the valve is only open for as short a period as possible in order to achieve the desired pulse, and thereafter the valve should close quickly to avoid the loss of high pressure air which has only marginal additional cleaning effect, but which adds to the cost of operation.
Where high pressure fluid is used to open the valve it is desirable that the pressure of that fluid is not so high that an operating pressure higher than that generally available within the plant where the equipment is located is required. It is generally desirable that the operating pressure required is somewhat lower than the pressure available at the plant so that even where the plant pressure fluctuates during the day, the operating pressure for the valve is still below the pressure available within the plant. Generally pressure of operation below about 80 psi (550 kPa) is desirable.
However, it is important that the operating system for opening the valve does not serve to decrease the efficiency of the valve by changing the opening speeds, or period of opening, of the valve. If by decreasing the operating pressure the overall efficiency of the valve were reduced, the net result for the system would be less than satisfactory.